|Pos|No|Driver|Constructor|Laps|Time/Retired|Grid|Points|
|---|---|---|---|---|---|---|---|
|1|7|Jo Bonnier|BRM|75|2:05:26.8|1|8|
|2|8|Jack Brabham|Cooper-Climax|75|+ 14.2|2|6|
|3|9|Masten Gregory|Cooper-Climax|75|+ 1:23.0|7|4|
|4|12|Innes Ireland|Lotus-Climax|74|+ 1 Lap|9|3|
|5|1|Jean Behra|Ferrari|74|+ 1 Lap|4|2|
|6|3|Phil Hill|Ferrari|73|+ 2 Laps|12||
|7|14|Graham Hill|Lotus-Climax|73|+ 2 Laps|5||
|8|10|Maurice Trintignant|Cooper-Climax|73|+ 2 Laps|11||
|9|16|Cliff Allison|Ferrari|71|+ 4 Laps|15||
|10|15|Carel Godin de Beaufort|Porsche|68|+ 7 Laps|14||
|Ret|11|Stirling Moss|Cooper-Climax|62|Gearbox|3|1|
|Ret|6|Harry Schell|BRM|46|Gearbox|6||
|Ret|2|Tony Brooks|Ferrari|42|Oil Leak|8||
|Ret|5|Carroll Shelby|Aston Martin|25|Engine|10||
|Ret|4|Roy Salvadori|Aston Martin|3|Engine|13||

Question: how many drivers are from the united states?
Answer: 4